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CELL CYCLES IN A COMPLEX MERISTEM AFTER X‐IRRADIATION
Author(s) -
CLOWES F. A. L.
Publication year - 1972
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1972.tb01969.x
Subject(s) - mitosis , meristem , biology , metaphase , irradiation , microbiology and biotechnology , botany , genetics , physics , chromosome , shoot , nuclear physics , gene
S ummary Mean rates of mitosis, determined over short intervals of time by blocking the cell cycle at metaphase, fall immediately after X‐irradiation in most parts of the root meristem of Zea mays. The fall continues for several hours and is then replaced by a rise until normal rates are reached. In the quiescent centre, however, the mean mitotic cycle shortens to one‐third of its previous duration within an hour of irradiation. The rate of mitosis then falls to nearly its previous level before rising again at the same time as the acceleration of the cycle in the other regions. Finally quiescence sets in again as the other regions return to greater mitotic activity. The observations suggest (1) that the reaction of the quiescent centre is not simply due to the relief of some inhibition imposed by the surrounding cells, (2) that something other than the different DNA levels of the various regions is in part responsible for the differential response, and (3) the resistance of the quiescent centre to irradiation is a real phenomenon requiring explanation.